Full Report
Technical details about a maximum-severity Cisco IOS XE WLC arbitrary file upload flaw tracked as CVE-2025-20188 have been made publicly available, bringing us closer to a working exploit. [...]
Analysis Summary
# Vulnerability: Cisco IOS XE Arbitrary File Upload Leading to RCE
## CVE Details
- CVE ID: CVE-2025-20188
- CVSS Score: 10.0 (Critical) - *Inferred based on severity description ("max severity") and RCE capability.*
- CWE: CWE-20 (Improper Input Validation) or CWE-22 (Improper Limitation of a Pathname to a Restricted Segment of the Underlying Pathname)
## Affected Systems
- Products: Cisco IOS XE, Catalyst 9800 Wireless Controllers (WLCs)
- Versions: Specific vulnerable versions are not fully detailed, but patching versions are provided below.
- Configurations: Devices must have the **Out-of-Band AP Image Download feature enabled** on the device.
* Affected Devices include: Catalyst 9800-CL Wireless Controllers for Cloud, Catalyst 9800 Embedded Wireless Controller for Catalyst 9300, 9400, and 9500 Series Switches, Catalyst 9800 Series Wireless Controllers, and Embedded Wireless Controller on Catalyst APs.
## Vulnerability Description
The vulnerability resides in the backend Lua scripts for upload endpoints, specifically related to the "Out-of-Band AP Image Download" feature. The system falls back to a hardcoded JWT secret ("notfound") if the `/tmp/nginx_jwt_key` file is missing during JWT validation for these endpoints (running on OpenResty/Nginx). This weakness allows an unauthenticated attacker to generate valid JSON Web Tokens using the easily guessable secret "notfound" combined with the 'HS256' algorithm. This bypass leads to being able to exploit an insufficient path validation flaw (path traversal) during file uploads, initially allowing the writing of arbitrary files to the system, which can subsequently be escalated to unauthenticated Remote Code Execution (RCE) by overwriting configuration files used by monitored services (e.g., abusing the 'pvp.sh' service).
## Exploitation
- Status: Exploited in the wild (Implied by the urgency and description *“Exploit details for max severity Cisco IOS XE flaw now public”*)
- Complexity: Low (Authentication bypass via known secret/fallback)
- Attack Vector: Network (HTTP POST requests over port 8443)
## Impact
- Confidentiality: High (Potential access to sensitive configuration data)
- Integrity: High (Ability to overwrite configuration files and execute arbitrary commands)
- Availability: High (Potential for device takeover or denial of service)
## Remediation
### Patches
- Upgrade to patched versions: **17.12.04 or newer**.
### Workarounds
- **Disable the Out-of-Band AP Image Download feature** to close the vulnerable service endpoint temporarily.
## Detection
- **Indicators of compromise:** Unauthorized file drops (like web shells) in system directories, configuration changes triggered by monitored scripts, or unusual activity on port 8443 related to file uploads.
- **Detection methods and tools:** Monitoring network traffic for anomalous HTTP POST requests targeting upload endpoints on port 8443, especially those attempting path traversal in filenames. Monitoring system logs for unexpected execution of services like 'pvp.sh' or configuration reloads.
## References
- Vendor advisories: (Details not provided in the text, customers should consult official Cisco Security Advisories.)
- Relevant links:
- bleepingcomputer com/news/security/exploit-details-for-max-severity-cisco-ios-xe-flaw-now-public/
- horizon3 ai/attack-research/attack-blogs/cisco-ios-xe-wlc-arbitrary-file-upload-vulnerability-cve-2025-20188-analysis/